Phosphate solubilizing rhizobacteria isolated from jujube ziziphus lotus plant stimulate wheat germination rate and seedlings growth

Jujube plant (Ziziphus lotus (L.) Desf.) can survive in arid climates and tolerates both biotic and abiotic stresses. Here, we isolated, for the first time in Morocco, nine phosphate solubilizing bacteria strains from jujube rhizosphere, designated J10 to J13, J15, & J153 to J156. Genotypic identification based on 16S rDNA sequencing, revealed six strains that belong to Pseudomonas (J10, J12, J13, J15, J153 and J154), two to Bacillus (J11 and J156), and one to Paenibacillus J155. Siderophores were produced by all strains. Proteases activity was missing in Pseudomonas sp. J153 & J154, whereas cellulase was restricted only to Pseudomonas sp. J10, Paenibacillus xylanexedens J155 and Bacillus cereus J156. Indole-3- acetic acid and ammonia were also produced by all strains, with a maxima of 204.28 mu g mL(-1) in Bacillus megaterium J11 and 0.33 mu mol mL(-1) in Pseudomonas sp. J153, respectively. Pseudomonas sp. J10 and B. cereus J156 grew on plates containing 1,500 mu g mL(-1) of nickel nitrate, while Pseudomonas sp. J153 withstood 1,500 mu g mL(-1) of either copper sulfate or cadmium sulfate. Phenotypic analysis of the potential of the isolates to promote early plant growth showed that wheat seeds inoculated with either P. moraviensis J12 or B. cereus J156 remarkably increased germination rate and seedlings growth. Lastly, antibiotic resistance profiling revealed that except for Pseudomonas sp. J11 and B. cereus J156, remaining strains displayed resistance at least to one of tested antibiotics. Collectively, Pseudomonas sp. J10, P. moraviensis J12, Pseudomonas sp. J153 and B. cereus J156, represent potential biofertilizers suitable for soils that are poor in P, and/or heavy metals contaminated.

Automated summary

In this study, nine phosphate solubilizing bacteria strains were isolated from the jujube rhizosphere in Morocco for the first time. These strains showed potential as biofertilizers to promote plant growth and resistance, especially in soils poor in phosphorus and/or heavy metals contamination.